Hello, I've been experimenting with BPF and BTF on small, emebedded platforms requiring cross-compilation to varying archs, word-sizes, and endianness. These environments are not the most common for the majority of eBPF users, and have exposed multiple problems with basic functionality. This patch series addresses some of these issues. Enabling BTF support in the kernel can sometimes result in sysfs export of /sys/kernel/btf/vmlinux as a zero-length file, which is still readable and seen to leak non-zero kernel data. Patch #1 adds a sanity-check to avoid this situation. Small systems commonly enable LD_DEAD_CODE_DATA_ELIMINATION, which causes the .BTF section data to be incorrectly removed and can trigger the problem above. Patch #2 preserves the BTF data. Even if BTF data is generated and embedded in the kernel, it may be encoded as non-native endianness due to another bug [1] currently being worked on. Patch #3 lets bpftool recognize the wrong BTF endianness rather than output a confusing/misleading ELF header error message. Patches #1 and #2 were first developed for Linux 5.4.x and should be backported if possible. Feedback and suggestions for improvement are welcome! Thanks, Tony [1] https://lore.kernel.org/bpf/CAPGftE8ipAacAnm9xMHFabXCL-XrCXGmOsX-Nsjvz9wnh3Zx-w@xxxxxxxxxxxxxx/ Tony Ambardar (3): bpf: fix sysfs export of empty BTF section bpf: prevent .BTF section elimination libbpf: fix native endian assumption when parsing BTF include/asm-generic/vmlinux.lds.h | 2 +- kernel/bpf/sysfs_btf.c | 6 +++--- tools/lib/bpf/btf.c | 6 ++++++ 3 files changed, 10 insertions(+), 4 deletions(-) -- 2.25.1
